MySQL/MariaDB

Common commands/use

mysql -e presumes that you have a .my.cnf in your user directory populated with the username and password of a user that has the privileges to do what you are doing. Such as: /root/.my.cnf

Otherwise, you would need to log into MySQL/MariaDB then execute the queries that are within the quotes.

Time and Date in MySQL/MariaDB

mysql -e "SELECT NOW();"

Show size of databases

mysql -e "SELECT table_schema AS 'Database Name', SUM(data_length + index_length) / 1024 / 1024 AS 'Database Size (MB)' FROM information_schema.TABLES GROUP BY table_schema;" | grep 'Database\|USERNAME_'

MyISAM table size & InnoDB table size

MYD+MYI = total MyISAM, ibdata1+ibd = total InnoDB. MYI are the MyISAM indexes, MYD is the MyISAM data.

lsof -u mysql|awk '$9~/\/var\/lib\/mysql\// {print $7, $9}'|awk -F'[/,.]' '{print $1, $NF}'|sort -k2|awk '{array[$2]+=$1} END {for (i in array) {print array[i]"\t"i}}'

You can also do this query, but it can trash the cache:

mysql -e "SELECT ENGINE,ROUND(SUM(data_length) /1024/1024, 1) AS 'Data MB', ROUND(SUM(index_length)/1024/1024, 1) AS 'Index MB', ROUND(SUM(data_length + index_length)/1024/1024, 1) AS 'Total MB', COUNT(*) 'Num Tables' FROM  INFORMATION_SCHEMA.TABLES WHERE  table_schema not in ('information_schema', 'performance_schema') GROUP BY ENGINE;"

Max Connections used

mysql -e 'show status;' | grep Max

Show compiled-in options

Binary options plus my.cnf and other option files:

mysqld --verbose --help

Binary options ignoring my.cnf and other option files:

mysqld --no-defaults --verbose --help

This also works for mysqldump, myisamchk, and anything else that you'll see as a header in my.cnf. For example:

mysqldump --verbose --help

Handy to see if "Dump Completed" message will be appended to .sql dump files:

mysqldump --verbose --help | grep 'comments\|dump-date'

Dumping and Importing

Dumping

mysqldump database_name > database_name.sql

Should append a "Dump completed on %date" at the end of each .sql file to show a successful dump. This is usually a binary option, but it it is not, set these in my.cnf:

comments

dump-date

Importing

CLI:

mysql database_name < database_name.sql

phpMyAdmin:

Import tab. Make sure that upload_filesize, post_max_size, and max_execution_time are generous enough in WHM >> Tweak Settings >> PHP for the import.

You usually need to drop a database before safely importing a .sql file. Dump the db, note its users and their privileges, recreate it, reassign the users and privileges, then import. If phpMyAdmin or cPanel is not available to you, then you need the MySQL users and passwords to see the privileges (easiest for noting).

Table-by-table dump for a single database

for table in `mysql DB  -e 'show tables;'| sed -n '1!p'`; do echo $table; mysqldump DB $table > DB.$table.sql ; done

Restore only one table from a .sql file

sed -n '/-- Table structure for table `'TABLE_NAME'`/,/-- Table/{ /^--.*$/d;p }' DUMPFILE.sql > DB.TABLE_NAME.sql

mysql DB < DB.TABLE_NAME.sql

Or try this:

sed -n -e '/-- Table structure for table `'"tablename"'`/,/UNLOCK TABLES/p' "databasename.sql" > "database.table.sql"

InnoDB Disabled?

If you run into relentless DB corruption:

mysqlcheck -Br roundcube

roundcube.cache

Error  : Incorrect information in file: './roundcube/cache.frm'

error  : Corrupt

roundcube.cache_index

Error  : Incorrect information in file: './roundcube/cache_index.frm'

error  : Corrupt

roundcube.cache_messages

Error  : Incorrect information in file: './roundcube/cache_messages.frm'

error  : Corrupt

InnoDB may be disabled. Try:

mysql -e "show engines;"

If InnoDB is disabled, check the error log for why. If you get something like this:

130424 06:18:09 mysqld restarted

130424 6:18:28 InnoDB: Error: cannot allocate 536887296 bytes of

InnoDB: memory with fakeuser! Total allocated memory

InnoDB: by InnoDB 8154720 bytes. Operating system errno: 12

InnoDB: Check if you should increase the swap file or

InnoDB: ulimits of your operating system.

InnoDB: On FreeBSD check you have compiled the OS with

InnoDB: a big enough maximum process size.

InnoDB: Note that in most 32-bit computers the process

InnoDB: memory space is limited to 2 GB or 4 GB.

InnoDB: We keep retrying the allocation for 60 seconds...

InnoDB: Fatal error: cannot allocate the memory for the buffer pool

130424 6:20:09 [Note] /usr/sbin/mysqld: ready for connections.

In this case, lower innodb_buffer_pool_size from 512M to a reasonable value.

Check stored procedures

phpMyAdmin >> SQL

show procedure status

See all db users

phpMyAdmin >> Privileges